1. Field of the invention
The present invention relates to a heat exchanger used in an air conditioning apparatus for an automobile, for instance, especially one that is constituted by a tank and tube elements assembled separately during assembly of the heat exchanger.
2. Description of the related art
A heat exchanger shown in FIGS. 10 and 11 is constituted by a tank and tube elements that are formed separately.
In the heat exchanger 1, a tank 10 comprises an end plate 12 and a tank member 13 in which a space is formed, the space being partitioned by a partition 11. Insertion holes 14 are formed in the end plate 12, and the tube elements 2 are inserted into the insertion holes 14. Each tube element 2 has an inner passage which is formed in a U-shape by a partitioning wall 2c, and intake/output openings 6, 6 are formed in a connecting portion 5 that is inserted into the insertion holes 14.
The heat exchanger 1 is constructed by a core of the heat exchanger being made by placing fins 3 between the tube elements 2 and inserting the connecting portion 5 of the tube elements 2 into the insertion holes 14, and then brazing the core in a furnace.
However, when the heat exchanger is brazed by the so-called heat brazing method, which is also called NB method, a method in which a non-corrode flux is applied to the core and then brazed in the furnace, because the furnace 30 used in the heat brazing method is low, as shown in FIG. 11, the core of the heat exchanger needs to lay sideways to be put into the furnace 30. In this case, because the elongate direction of the insertion holes 14 in which the tube elements 2 are inserted is perpendicular to the horizontal, a brazing filler material of the surface of the end plate 12 flows along the edge of the insertion hole 14 in the perpendicularly downward direction by the gravity. Furthermore, because it is difficult to perfectly form the insertion holes 14 of the end plate 12 along the periphery of the connecting portion 5 of the tube elements 2, gaps A may be easily formed between the insertion holes 14 and the tube element 2 easily as shown in FIG. 12.
Thus, when the brazing filler material flows along the periphery of the insertion holes 14 in the downward direction, the gaps A between the insertion holes 14, especially at the upper portion of the insertion holes 14 and the connecting portion 5 of the tube elements 2, may easily lack brazing filler material. Lacking the brazing filler material causes poor bonding between the tank 10 and tube elements 2 and the problem that a heat exchanging medium can leak out from the portion lacking brazing filler material.